Which of the following is a flow-assisted corrosion mechanism?

• A. Erosion-corrosion
• B. Pitting
• C. Crevice
• D. Hydrogen-induced cracking

Answer: (A)

Flow-assisted corrosion occurs when moving fluid interacts with the surface to speed up material loss beyond what chemical attack alone would cause. Erosion by the flowing medium mechanically wears away protective films and pushes away corrosion products, exposing fresh metal and accelerating overall corrosion. This synergistic effect is exactly what erosion-corrosion describes, making it the clear example of a flow-assisted mechanism. Pitting and crevice corrosion are driven more by localized chemistry and restricted areas where stagnant or differential conditions exist, not by the direct action of flowing fluid. Hydrogen-induced cracking is a hydrogen embrittlement process under stress, not a flow-enhanced corrosion mechanism.